Outcomes and Imaging Analysis in Hepatocellular Carcinoma Treated with Stereotactic Body Radiation Therapy

Purpose/Objective(s)

Although arterial phase enhancement is commonly used to evaluate treatment response for hepatocellular carcinoma (HCC), it may not accurately describe response for lesions treated with stereotactic body radiation therapy (SBRT). We aimed to describe the post-SBRT imaging findings to better understand the kinetics of radiographic resolution of HCC and to better inform the optimal timing of salvage therapy after SBRT.

Materials/Methods

We retrospectively reviewed the records of patients with HCC treated with SBRT from 2006 to 2021 at a single institution with available triphasic imaging. We included lesions with characteristic arterial enhancement and portal venous and delayed venous phase washout on initial staging scans. Patients were then stratified into three groups based on treatment: 1) concurrent SBRT and TACE, 2) SBRT only, and 3) SBRT followed by early salvage therapy due to persistent enhancement. Overall survival (OS) was analyzed with Kaplan-Meier, and cumulative incidence of local failure (LF) was calculated with competing risk analysis with death.

Results

We included 82 liver lesions in 73 patients. Median follow-up time was 22.3 months (range 2.2-88.1 months). Median time to OS for the entire cohort was 43.7 months (95% CI 18.1-57.6 months) and median progression free survival was 9.5 months (95% CI 6.3-14.0 months). There are a total of 11 (13.4%) lesions that experienced LF in the entire cohort, and cumulative incidence of LF was not significantly different between the 3 groups (p=0.3257). In the SBRT only group, the median time to resolution of arterial enhancement and washout was 5.3 months (range 1.6-23.7 months). At 3, 6, 9, and 12 months, 82%, 41%, 13%, and 8% of lesions continued to show arterial hyperenhancement.

Conclusion

Tumors treated with SBRT may continue to exhibit persistence of arterial hyperenhancement. Without an increase in size of enhancement, continued surveillance, rather than early salvage therapy, may be appropriate for these patients.